Skip to main content

Full text of "Preliminary investigation of the mineralogical composition of the stone meteorite Venerova"

See other formats





NASA TT F-10,213 


I, A. Yudin 

Translation of "Predvaritel 'noye issledovaniye mineralogicheskogo 
sostava kamennogo meteorita Vengerovo" 
Doklady Akademii Nauk SSSR, 
Vol. 84, No. 1, pp. 123-126, 1952 


Hard copy (HC) y^ ^^"^ 
Microfiche <Mi=l .^6Z) 

N66 29729 






ff e53 Jutv 65 


JUNE 1966 

NASA TT F-10,213 



I. A. Yudin 



Composition of the meteorite is analyzed loy size, shape, 
structure and ore (or silicate) content. Etching, micro- 
scopy, and spectral and chemical aaalysis are used. 

A stone meteorite dropped to the ground in the Vengerovo district of /l23' ^ 
the Novosibirsk oblast on 11 October I95O at lA\h3. Acting on instructions from 
the Committee on Meteorites of the USSR Academy of Sciences and with the coop- 
eration of Prof. A. Ye. MalaJdaov, the author collected some observation data 
and meteorites in the autiimn of that year (ref. l). Those efforts were con- 
tinued in Jiily 1951 • 

The local residents had found tvo separate specimens. The larger one 
weighed 9.3 kg and had a half-oriented shape. One side of the meteorite had 
a pyramidal habit and was covered with a black crust of fusion of the first 
genus with distinct glyptic lines; its ed^es were blunted and rounded. This 
was apparently the front side . It was facing downward when the meteorite was 
lying in^pit. The back side of the meteorite was flat with an irregular angu- 

larity and covered with a crust of the second genus, 


•^Numbers given in margin indicate pagination in original fox-elgn text. 

NASA TT F-10,213 

Only a small fragment, partially stripped and weighing 27 g^ was left of 
the second specimen which, according to the finder, had weighed over 1 kg. 

The author made a mineralographic investigation of the meteorite in the 
laboratory of ore-deposit geology of the Sverdlovsk Mining Institute \inder the 
supervision of Prof. S. A. Vakhromeyev. A small fragment of the larger speci- 
men was used in the tests. 

The fresh fracture revealed the bulk of the meteorite to be of a light 
gray color; black thread veinlets were observable in some parts. Structurally 
it was a typical chondrite with macroscopically visible chondrules up to several 
millimeters in size, as well as plessite inclusions, one of which had a diameter 
of 0.5 cm' there were traces of troilite . 

Three polished and two petrographic sections were prepared for micro- 
scopic examination. The following ore minerals were identified in the meteo- 
rite under the microscope in a reflected light: plessite, troilite, chromite and 
native copper . 

The plessite is main ore mineral, and it amounts to from 6 to 10 percent 
by volume. Relatively large grains, measuring from 0.10 to OA mm, are pre- 
dominantj they have an irregular angular shape with occasional corroded ser- 
rated edges. An etching test with a 6 percent solution of nitric acid re- 
vealed a granular structure in the plessite. A light fringe several microns 
vide apparently consisting of taenite was observable on the grain periphery 
after the etching. The central part of the grain was dark with a shagreen 
surface and probably consisted of plessite. 

There were, in addition to the plessite inclusions, tiny dust-like /l24 
formations of an isometric or drop-shaped form measuring from tenth parts of a 
micron to several microns. Similar formations were observed both in the grotind 

mass of the meteorite and in the silicate chondrules. These formations were 
evenly scattered in the chondrules^ but the droplets were more frequently con- 
centrated in the center of the chondrule or along its periphery- In most cases 
the droplets were observable in the darker silicate portion of the meteorite. 

In very rare cases the intergrowth of plessite with troilite results in 
the formation of very thin veinlets, about 1-2M» thick, which are usually con- 
fined to the black meteorite veins observable under a microscope. 

The troilite content in the meteorite was 3.I+ to 3.7 percent by volinne. 
By the shape of its grains, troilite is very similar to plessite- These two 
minerals usually occur together, and are frequently intergrown. Special men- 
tion should be made of the inclusions of small troilite grains in the plessite, 
which are as a rule associated with native copper. Such grains usually have 
an irregular shape with angular corroded edges. Some of the grains are slightly 
elongated, their sizes varying from tenth parts of a micron to several microns. 
Such floating troilite "chips" in the plessite, as it were, are relatively rare. 

Figure 1. Troilite grain (2) surrounded by a plessite 
fringe (3),, 1-silicates. Polished microsection 22; 
reflected light; magnification 3OO. 

The plessite containing them is almost always intergrown vith the large troilite 
grains. Troilite grains with a plessite edge along the periphery are encoun- 
tered very seldom (fig. l). 

More or less round or oval troilite inclusions are occasionally found in 
these macroscopic black veinlets of the meteorite. These inclusions^ in turn^ 
contain tiny teardrop -shaped plessite grains measuring several microns. 

The chromite content in the meteorite is insignificant^ varying from 0.2 
to 0.3 percent by volume. Predominant among them are grains measuring 0.0^ 
to O.OOU mm, with the same irregular and angular shape as the plessite and 
troilite grains. There is a fairly vide occurrence in the meteorite of iso- 
metric and teardrop-shaped chromite formations, ranging in size from tenth 
parts of a micron to several microns. In most cases they are enclosed in the 
silicate chondiniles (fig. 2, inset). Little chains of chromite with plessite 
droplets are occasionally seen surrounding the chondrules; they also occur in 
the main silicate part of the meteorite. Tiny teardrop- shaped formations of 
chromite are also found in the plessite. 

The native copper found in the meteorite was determined by the following 
indications: the freshly cut and polished surface was copper- colored but turned 
to an intense red a few hours later because of its oxidation in the air; the 
reflection index was higher than that of the plessite, R "^ 90 percent; it had 
a high luster; its hardness was lower than that of plessite; as the micro- /l2^ 
scope table is raised, the luminous line shifts from the copper to the plessite 

...r^ HCl Cl'l) 

it is isotropic. A diagnostic etching with HNO^ (l:l) has produced negative 
results, and the use of HgCl 5 percent and FeCl 20 percent produced positive 
resiilts: the native copper began to turn black at a fast rate. 



/ 1 



Figiire 2, Tiny teardrop- shaped 
chromite inclusions (light gray) 
in a silicate chondmle. Arrows 
indicate teardrop -shaped inclu- 
sions of plessite (white); sili- 
cates are shown in black. Pol- 
ished microsection 22; reflected 
light; magnification 600. 



\ * 

i i 




Figure 3. Oxidized native copper 
grains (blacky indicated by ar- 
row) included in the plessite 
(white). The gray color indi- 
cates troilite, and the black 
silicates. Polished microsec- 
tion 3U; reflected light; magni- 
fication 600. 

A spectral analysis of the meteorite revealed faint copper lines (table l) 
A complete chemical analysis of the meteorite established a copper content of 
0.06 percent. 

The native copper grains are associated with troilite and plessite. The 
copper practically always occurs in the form of tiny inclusions in plessite 
where it is intergrown with small troilite grains to some extent or other 
(fig. 3). In only one case was it possible to find native copper inclusions 

"knae analysis was made by L. N. Zakharova. 


m^ ^^ lZj^ Si^ I 

Figure k. Native copper (k) intergrown with troilite 
(2) and pies site (3)^ 1-silicates- Polished micro- 
section 34; magnification 65O. 

on the face of the intergrowth of relatively large troilite and pies site forma- 
tions (fig. U) . 

The grains of the native copper are irregular in shape and in most cases 
elongated. Minute offsets^ visible only under large microscopic magnification 
when immersed in oil^ extend from the grain edges in some areas. 

The author made a thoroiogh examination of three highly magnified polished 

surfaces with a total area of 5 cm , but found no native copper in the plessite 

grains which did not contain any troilite *'chips." 

The copper grains are very small in size^ measuring not more than O.O3 mm 
in length and up to 0.01 mm in width, but they usually do not exceed 1/m». 

A spectral analysis of the meteorite produced the following results 

Analysis by N. Yarosh. 

HAS A TT F-10,213 


Mn weak 

Mg very intense 

Si intense 

Fe intense 

Co weak + 

Ni medium 

Cr medium high 

AL intense 

V weak 

Ti weak + 

Ha medium 

Cu weak 

Ca intense 

The nonn^talliferous part of the meteorite consists of the following 
silicates: olivine^ pyroxene and vitreous mass. A microscopic examination 
revealed the following textures of the silicate chondrules : microporphyritic, 
grizzled, eccentrically radiated and polygonal-granular; the chondrules are 
round in shape. Some silicate chondrules are enclosed in a shell consisting 
of tiny troilite and plessite inclusions. 

1. Yudin, I. A. 

Priroda, No. 8, 3O, I95I